Chaos in circuit QED: decoherence, localization, and nonclassicality

TL;DR

This paper investigates how measurement-induced decoherence influences quantum chaos in a circuit QED system, revealing that quantum correlations prevent classical-like localization even under strong measurement, contrasting with previous studies.

Contribution

It demonstrates that quantum correlations in circuit QED prevent classical localization in chaotic dynamics despite measurement-induced decoherence.

Findings

Measurement causes localization in single realizations but not in ensembles.

Quantum correlations persist despite decoherence, hindering classical correspondence.

Classical chaos is not fully recovered in the quantum regime under measurement.

Abstract

We study the open system dynamics of a circuit QED model operating in the ultrastrong coupling regime. If the resonator is pumped periodically in time the underlying classical system is chaotic. Indeed, the periodically driven Jaynes-Cummings model in the Born-Oppenheimer approximation resembles a Duffing oscillator which in the classical limit is a well-known example of a chaotic system. Detection of the field quadrature of the output field acts as an effective position measurement of the oscillator. We address how such detection affects the quantum chaotic evolution in this bipartite system. We differentiate between single measurement realizations and ensembles of repeated measurements. In the former case a measurement/decoherence induced localization effect is encountered, while in the latter this localization is almost completely absent. This is in marked contrast to numerous earlier works discussing the quantum-classical correspondence in measured chaotic systems. This lack of a classical correspondence under relatively strong measurement induced decoherence is attributed to the inherent quantum nature of the qubit subsystem and in particular to the quantum correlations between the qubit and the field which persist despite the decoherence.